Hot melt acrylic pressure sensitive adhesive and use thereof

Abstract

The present invention provides a hot melt acrylic pressure sensitive adhesive (PSA) comprising an acrylic polymer having units derived from one or more C 1 -C 20 alkyl esters of acrylic or methacrylic acid and units derived from one or more vinyl esters corresponding to the formula (I), wherein R 1 , R 2 and R 3 each independently represent an alkyl group and the total number of carbon atoms in the vinyl ester is from 7 to 18. The PSA is particularly suitable for sticking objects to a low surface energy substrate.

1 . A method of using a hot melt acrylic pressure sensitive adhesive for adhering an object to a low surface energy substrate having a surface tension of not more than 40 mN/m, said hot melt acrylic pressure sensitive adhesive comprising an acrylic polymer having units derived from one or more C 1 -C 20  alkyl esters of acrylic or methacrylic acid and units derived from one or more vinyl esters corresponding to the formula:  
     
       
         
         
             
             
         
       
     
     wherein R 1 , R 2  and R 3  each independently represent an alkyl group and the total number of carbon atoms in the vinyl ester is from 7 to 18.  
   
   
       2 . The method according to  claim 1  wherein at least one of R 1 , R 2  and R 3  represents a methyl group.  
   
   
       3 . The method according to  claim 1  wherein said low surface energy substrate is selected from the group consisting of a polyolefin substrate, a painted metal substrate or a painted plastic substrate.  
   
   
       4 . The method according to  claim 1  wherein said object comprises a sheet material.  
   
   
       5 . The method according to  claim 1  wherein the amount of units derived from said C 1 -C 20  alkyl esters of acrylic or methacrylic acid is between 30 and 90% by weight and the amount of said vinyl esters of formula (I) is between 10 and 70% by weight.  
   
   
       6 . The method according to  claim 4  wherein said acrylic polymer further comprises units derived from acrylic and/or methacrylic acid in an amount of 0.5 to 10% by weight and optionally between 0 and 20% by weight of further comonomers.  
   
   
       7 . The method according to  claim 1  wherein the acrylic copolymer comprises at least 10% by mole of triads solely formed by units derived from said vinyl esters.  
   
   
       8 . The method according to any of the previous claims wherein a layer of said hot melt pressure sensitive adhesive is applied to said object or to said low surface energy substrate and said object is adhered to said low surface energy substrate by application of pressure.  
   
   
       9 . An adhesive composition for application to a substrate by melt extruding the adhesive composition on said substrate, wherein said adhesive composition comprised a composition substantially free of organic solvent or water, said adhesive composition comprising an acrylic polymer having between 0.5 and 10% by weight of units derived from acrylic and/or methacrylic acid, between 10 and 70% by weight of units derived from one or more vinyl esters according to formula (I) defined in  claim 1 , between 30 and 90% by weight of units derived from one or more C 1 -C 20  alkyl esters of acrylic or methacrylic acid and between 0 and 20% by weight of units derived from optional further comonomers.  
   
   
       10 . The adhesive composition according to  claim 9  wherein said adhesive composition is combined with a packaging material.  
   
   
       11 . The adhesive composition according to  claim 9  wherein said adhesive composition is packaged in a packaging material that can be melt extruded and that when melt extruded together with the adhesive composition does not destroy the adhesiveness of the composition.  
   
   
       12 . A method for making an adhesive article comprising the steps of melt extruding an adhesive composition according to  claim 9  on a substrate to form a pressure sensitive adhesive layer thereon.  
   
   
       13 . The method according to  claim 12  wherein said method further comprises the step of laminating said pressure sensitive adhesive layer to a further substrate.  
   
   
       14 . The method according to  claim 13  wherein said step of laminating transfers said pressure sensitive adhesive layer to said further substrate.  
   
   
       15 . The method according to  claim 12  wherein said substrate comprises a polyvinyl chloride film or a polyolefin film.  
   
   
       16 . The method according to  claim 13  wherein said further substrate comprises a polyvinyl chloride film or a polyolefin film.  
   
   
       17 . A method of making an adhesive composition according to  claim 9  comprising the steps of: 
 (c) providing a pre-adhesive composition that comprises (i) a monomer mixture consisting of 0.5 to 10% by weight of acrylic and/or methacrylic acid, between 10 and 70% by weight of one or more vinyl esters according to formula (I) defined in  claim 1 , between 30 and 90% by weight of one or more C 1 -C 20  alkyl esters of acrylic or methacrylic acid and between 0 and 20% by weight of optional further comonomers, (ii) optionally one or more free radical initiators and (iii) optionally one or more chain transfer agents;    (d) and polymerizing said pre-adhesive composition by exposing said pre-adhesive composition to heat and/or actinic radiation.    
   
   
       18 . The method according to  claim 17  wherein said pre-adhesive composition is combined with a packaging material.  
   
   
       19 . The method according to  claim 18  wherein said packaging material is as defined in  claim 11 .  
   
   
       20 . A pre-adhesive composition comprising (i) a monomer mixture consisting of 0.5 to 10% by weight of acrylic and/or methacrylic acid, between 10 and 70% by weight of one or more vinyl esters according to formula (I) defined above, between 30 and 90% by weight of one or more C 1 -C 20  alkyl esters of acrylic or methacrylic acid and between 0 and 20% by weight of optional further comonomers, (ii) one or more free radical initiators and (iii) optionally one or more chain transfer agents.  
   
   
       21 . A pre-adhesive composition according to  claim 20  wherein said pre-adhesive composition is combined with a packaging material as defined in  claim 11.